Cardiology · Arrhythmias
The facts most likely to be tested
Premature ventricular contractions (PVCs) appear on ECG as wide, bizarre QRS complexes that occur earlier than the next expected sinus beat.
The compensatory pause following a PVC occurs because the sinus node is not reset by the retrograde conduction of the ventricular impulse.
Asymptomatic patients with a structurally normal heart and PVCs require no pharmacological treatment or further intervention.
Symptomatic patients with PVCs should be evaluated with an echocardiogram to rule out underlying structural heart disease or cardiomyopathy.
Beta-blockers or calcium channel blockers are the first-line pharmacologic therapy for symptomatic patients with PVCs.
Frequent PVCs (typically >10-15% of total beats) can lead to PVC-induced cardiomyopathy, which is reversible with successful catheter ablation.
PVCs originating from the right ventricular outflow tract (RVOT) typically exhibit a left bundle branch block (LBBB) pattern with an inferior axis.
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A 45-year-old male presents to the clinic complaining of 'skipped beats' and a fluttering sensation in his chest. He denies syncope, chest pain, or shortness of breath. His physical exam is unremarkable, and his blood pressure is 125/80 mmHg. An ECG reveals a normal sinus rhythm interrupted by wide QRS complexes followed by a compensatory pause. An echocardiogram is performed and shows a normal ejection fraction with no structural abnormalities.
What is the most appropriate management for this patient?
Reassurance and lifestyle modification
The patient has symptomatic PVCs but a structurally normal heart on echocardiogram, which carries a benign prognosis and requires no antiarrhythmic therapy.
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Etiology / Epidemiology
Common in structural heart disease, electrolyte imbalances, and caffeine/stimulant use.
Clinical Manifestations
Patients report palpitations or a skipped beat sensation; usually asymptomatic.
Diagnosis
ECG shows wide, bizarre QRS complexes without a preceding P-wave.
Treatment
Asymptomatic patients require observation; symptomatic patients receive beta-blockers.
Prognosis
Frequent PVCs (>10-15% of beats) may lead to PVC-induced cardiomyopathy.
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Epidemiology & Etiology
PVCs are ubiquitous in both healthy individuals and those with ischemic heart disease. Common triggers include hypokalemia, hypomagnesemia, and excessive intake of sympathomimetics. Increased frequency is often noted in patients with left ventricular hypertrophy or prior myocardial infarction.
Pertinent Anatomy
Originates from an ectopic focus within the ventricles, bypassing the normal His-Purkinje conduction system. This results in abnormal, slow cell-to-cell depolarization.
Pathophysiology
An ectopic ventricular focus fires prematurely, causing a wide QRS complex. This is followed by a compensatory pause because the sinus node is reset by the retrograde conduction. Frequent ectopy can lead to ventricular dyssynchrony and reduced cardiac output.
Clinical Manifestations
Patients often describe a thumping sensation in the chest or a feeling of a missed beat. Physical exam may reveal an irregularly irregular pulse or a pulse deficit. Red flags include syncope, chest pain, or dyspnea, which necessitate urgent evaluation for ventricular tachycardia.
Diagnosis
The 12-lead ECG is the diagnostic tool of choice. Findings include a wide QRS complex (>120 ms) with a discordant T-wave and no associated P-wave. A Holter monitor is indicated if the burden of PVCs is suspected to be high or if the patient is symptomatic.
Treatment
Asymptomatic patients require no intervention beyond lifestyle modification (caffeine/alcohol reduction). Symptomatic patients are treated with beta-blockers as the first-line therapy. Contraindications for beta-blockers include severe bradycardia or decompensated heart failure. Ablation is reserved for patients with refractory symptoms or PVC-induced cardiomyopathy.
Prognosis
Most PVCs are benign, but a high burden (>10,000-20,000/day) is associated with left ventricular dysfunction. Patients with structural heart disease and frequent PVCs require echocardiography to assess for underlying cardiomyopathy.
Differential Diagnosis
Atrial Premature Beats: Narrow QRS complex with a visible P-wave
Ventricular Tachycardia: Three or more consecutive PVCs at >100 bpm
Wolff-Parkinson-White: Presence of a delta wave on ECG
Bundle Branch Block: Wide QRS with a fixed, non-premature morphology
Electrolyte Disturbance: Often presents with associated U-waves or peaked T-waves